The long term goal of this project is to understand the molecular chemistry of multicenter metalloproteins, particularly cytochrome oxidase and related hemoproteins, and to uncover fundamental new chemical phenomena related to such systems. A synthetic model compound approach is taken which emphasizes the definitive characterization of binucleating porphyrins which hold two metals in close proximity. Iron porphyrins with chelated copper will serve as cytochrome oxidase models; a more diverse selection of metals will allow an exploration of new structural and chemical reactivity aspects that are unique to binuclear systems. Particular emphasis will be placed on understanding spin-coupling phenomena in paramagnetic metal/metal and metal/ligand radical systems. The investigative techniques of single crystal X-ray structure determination and variable temperature magnetic susceptibility will be emphasized along with a variety of spectroscopic techniques (IR, UV-VIS Mossbauer, EPR, etc.). A detailed molecular level understanding of hemoproteins and related metalloproteins is based on fundamental chemical principles and must underlie medical approaches to the therapy of metalloprotein disorders (thalassemias, sickle cell anemia, etc.).